Alkyleneimine adducts of trisacrylylhexahydro-s-triazine



United States Patent 3,526,625 ALKYLENEIMINE ADDUCTS 0F TRIS-ACRYLYLHEXAHYDRO-s-TRIAZINE Joseph Adrian Hoffman, Bound Brook, N.J.,assignor to American Cyauamid Company, Stamford, Conn., a corporation ofMaine No Drawing. Filed Aug. 25, 1966, Ser. No. 574,936 The portion ofthe term of the patent subsequent to Dec. 17, 1985, has been disclaimedInt. Cl. C07d 55/14 U.S. Cl. 260-248 1 Claim ABSTRACT OF THE DISCLOSURE1,3,5 tris(;8-(alkylaziridinyl)propionyl)-hexahydro-striazines of thestructure:

wherein the Rs are individually selected from the group consisting ofhydrogen and lower alkyl and at least one of R R is other than hydrogen,and their use as crosslinking agents, particularly for elastomers.

This invention relates to and has as its object the provision of a classof new compounds, and from a utility standpoint, to their use ascross-linking agents. More particularly, it relates to1,3,5-tris(fl-(alkylaziridinyl') propionyl)-hexahydro-s-triazines of thestructure:

wherein the Rs are individually selected from the group consisting ofhydrogen and lower alkyl and at least one of R -R is other thanhydrogen. It also relates to the use of the compounds of the abovestructure as crosslinking agents, particularly for elastomers.

The compounds of this invention can be prepared by reacting one mole ofa l,3,5-tris(acrylyl or alkylacrylyl)- hexahydro-s-triazine with threemoles of an alkyl aziridine. The l,3,5-tris(acrylyl or alkylacr'ylyl)hexahydro-striazines may be prepared by reacting formaldehydewith acrylonitrile or alkylacrylonitrile in the presence of concentrated sulfuric acid as described in U.S. Pat. 2,559,- 835. Forexample, 1,3, -tris(methacrylyl)hexahydro-striazine may be made byreacting methacrylonitrile with paraformaldehyde in the presence ofconcentrated sulfuric acid.

The alkylaziridines which may be used include 2-methylaziridine,Z-ethylaziridine, 2,3-dimethylaziridine, 2,2-dimethylaziridine, etc.2,2,3,3-tetraalkylaziridines may be prepared by the process described inJ. Am. Chem. Soc., 82, 6068-70 (1960) and are useful in the presetinvention.

While three moles of alkylaziridine are required for complete reactionwith one mole of 1,3,5-tris(acrylyl oralkylacrylyl)hexahydro-s-triazine, it is preferred to employ an excessof the alkylaziridine, said excess serving to ensure complete reactionand as a reaction medium. The particular amount of excess alkylaziridineis not especially critical since it is stripped from the reactionmixture and recovered. Generally the amount of alkylaziridine will beabout double the molar quantity required. The reaction is convenientlycarried out at room temperature for about 24 hours after which theexcess alkylaziridine is stripped 01f under vacuum.

Compounds of Formula I are moderately viscous mobile liquids. Afterremoval of excess alkylaziridine, the products are usually ofsatisfactory purity for normal use as cross-linking agents and arestable for long time periods at room temperatures, without the presenceof an inhibitor.

The products of this invention contain three aziridinyl groups and arereactive with monomeric and polymeric compounds having reactivehydrogens, including alcohols, phenols, mercaptans, thiophenols,carboxylic acids, amines, etc. They are thus useful as cross-linkingagents in the preparation of plastics and resins, textiles, varnishes,paper, etc. For example, they are effective curing agents :forvulcanizable rubbery materials which serve as binders in solid rocketpropellant compositions. Rubbery materials include homopolymers ofconjugated dienes and copolymers of conjugated dienes with materialscopolymerizable therewith, as shown in U.S. Pat. 3,087,843. Ofparticular interest is their use in propellant compositions comprisingan inorganic oxidizing salt and either a synthetic acid-terminatedpolymeric binder or a synthetic copolymer of a conjugated diene and anunsaturated carboxylic acid (see U.S. Pat. No. 3,087,844). The firsttype of polymer may be exemplified by the formula:

wherein Q is a polymer chain, as for example, a polymer of a conjugateddiene such as 1,3-butadiene. The second type of polymer may beexemplified by a copolymer of 1,3-butadiene and acrylic acid.

The compounds of the present invention are extremely useful as curingagents for the rocket propellant compositions described above, whereadvantage is taken of their liquid nature for ready incorporationtherein, and of their comparative slow curing rates for extendedpotlives.

It is surprising that the compounds of the present invention whichcontain substituted aziridine groups should have ready solubility inbutadiene polymers of the acid terminated type while their counterpartscontaining unsubstituted aziridine groups should not. It is alsosurprising that the compounds of the present invention should be liquidsat normal temperatures while the counterparts containing unsubstitutedaziridine groups should not.

To ensure thorough blending of the cross-linking agent with the polymerat temperatures which do not seriously reduce pot-life of the polymer,it is essential that the cross-linking agents be liquid and readilysoluble in the polymer at normal temperatures. The compounds containingunsubstituted aziridine groups are solids at ordinary temperatures andare not readily soluble in the polymer. Use of heat to effect solutionof the compounds containing unsubstituted aziridine groups reducespot-life below necessary requirements because of the fast reactivity ofthis compound type with the polymer even though the compound is notcompletely dissolved. The utility of compounds containing unsubstitutedaziridine groups in the particular polymer type thus is not feasible.The compounds of the present invention, however, under the sameconditions of use are readily soluble 3 in the polymer and provideadequate pot-life, i.e., in excess of twelve hours.

The invention is more fully illustrated by the examples which follow. Inthese examples the parts and percentages are by weight unless otherwiseindicated.

EXAMPLE 1 EXAMPLE 2 Following the procedure of Example 1 butsubstituting 426 parts (6 moles) of Z-ethylaziridine for theZ-methylaziridine therein, there was obtained a similar product.

EXAMPLE 3 Following the procedure of Example 1 but substituting 426parts (6 moles) of 2,3-dimethylaziridine for the 2- methylaziridinetherein, there was obtained a similar product.

EXAMPLE 4 Various of the substituted aziridine-containing compounds wereevaluated as cross-linking agents in a carboxy-terminated polymer of1,3-butadiene by incorporation therein and determining the time forgelation. An unsubstituted aziridine containing compound was compared.The results are given in the table below. Usage of the cross-linkingagent was one equivalent per equivalent of polymer.

4 TABLEI Relative curing rates of various aziridinyl compounds Compound:Time for gelation (hours) Example 1 (2-methy1 derivative) 24 Example 2(2-ethyl derivative) 48 Example 3 (2,3-dimethyl derivative) 36 1,3,5tris (1-aziridinyl)propionyl hexahydro-striazine 1 (Prior Art Compound)(U.S. 2,651,-

wherein R, R R R and R are each individually selected from the groupconsisting of hydrogen and lower alkyl and wherein at least one of R R Rand R is lower alkyl.

References Cited UNITED STATES PATENTS 2,651,631 9/1953 Zerner et al.260--248 3,417,059 12/1968 Hofiman 260248 XR HENRY R. JILES, PrimaryExaminer J M. FORD, Assistant Examiner US. Cl. X.R.

